Telephone system



1933. s. v. SMITH TELEPHONE SYSTEM Filed April 27. 1932 11 Sheets-Sheet 1 mum INVENTOR G. l. SM/T J @QM ATTORMEV 06L l0, V. sMn' TELEPHONE SYSTEM Filed April 2'7. 1932 11 Sheets-Sheet 2 lNl/ENTOR By a. I/SM/TH ATTORNEY Oct. 10, 1933. G. v. SMITH TELEPHONE SYSTEM Filed April 27. 1932 11 Sheets-Sheet 3 QR n.2

IN VE N TOR NR I ATTOPMEV Oct. 10, 1933.

G. V. SMITH TELEPHONE SYSTEM Filed April 27. 1932 11 Sheets-Sheet 4 lNVENTOR By G. L SM/TH ATTORNEY Oct. 10, 1933. v s rr TELEPHONE sYsTEu Filed April 27. 1952 11 Sheets-Sheet 5 INVEN TOR G. I/ SMITH By M ATTORNEY Get. 10, 1933. G. v. SMITH 1,930,255

TELEPHONE SYSTEM Filed April 27. 1952 ll Sheets-Sheet 6 FIG. 6'

8 P, INVENTOR w m w G. l/ SM/TH ATTORNEY Oct. 10, 1933. v sum- 1,930,255

TELEPHONE SYSTEM Filed April 27. 1932 '11 Sheets-Sheet 'z INVENTOR G. 1! SMITH ATTORNEY Qci. w, 193". G. v. SMITH TELEPHONE SYSTEM Filed April 27. 1932 ll Sheets-Sheet 8 IN VENT 0R 5 a. L .SM/TH ATTORNEY Oct. 10, 1933. e. v. SMITH 1,930,255

TELEPHONE SYSTEM Filed April 27. 1932 11 Sheets-Sheet 9 U U U U U U U U INVENTOR G. L 5114/ TH By $16M lg I ATTORNEY Filed April 27. 1932 ll Sheets-Sheet 10 NMQ INVENTOR G. l. SM/TH 6? 61 M ATTORNEY Oct. 10, 1933.

MARGINAL G. V. SMITH TELEPHONE SYSTEM Filed April 27. 1932 11 Sheets-Sheet ll INVENTOR G. L SMITH By $6M ATTORNEY UNITED STATES PAT'JENT OFFICE TELEPHONE SYSTEM Gerard V. Smith, White Plains, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N.'Y., a corporation of New York Application April 27, 1932. Serial No. 607,695

11 Claims. (01. 179-27) 7 This invention relates to telephone exchange in selector switches. These trunks are assosystems and moreparticularly to dial switching ciable by means. of three-way link circuits with systems-in which operators are. employed for exthe position, circuits of B operators and senders tending calls originating in manual oflices of common to all B operators positionsof theYof-' the exchange area to subscribers lines in a dial fice. 'Whenever a call is incoming on one. of. the switching office and in which operators are emtrunk circuits, such trunk circuit is automatically ployed for givingspecial service to subscribers connectedby a link circuitwithan idle sender such as service onintercepted calls. and with an idle Boperators position, the :B1

In some ofiices it is desirable because of ecooperator being listened-in automatically to renomical reasons .to combine the positions of A ceive instructions for terminating the ..call.*

operators whoattend to intercepted calls and Should the B operators position whichvisadjacall distributing B operators positions upon a cent to an A operators position be vacated, for single switchboard. In such a combined switchexample, at night, such position is normally. renboard, it is possible to. secure the greatest operdered unselectable to incoming trunkv calls. In

5;ating eiiiciency by. enabling the B operator whose accordance. with the present invention, however, 7 position is adjacent to an A operators position a key is provided on the B operators keyshelf on the same switchboard, to assist in handling which is accessible to the. adjacent A operator, intercepted calls at such times as calls incoming which. the.A operator may depress when the B to her position for termination in the dial switchposition is vacated and a call exists on a trunk 20 mg equipment of the oifice in which she is 10- incoming to the B position thereby causing the sated. are few, or to permit an intercepting A disconnection of the Aoperators telephone set operator, "whose position is adjacent to. a. call from normal association with the cord circuits distributing B opcrators position, to handle calls of. her position, the connection of the telephone for intercepted serviceon her own position and set with the position circuit of the vacated 'B -5 calls incoming for termination on the B operaposition and causing. the B position to again be- I torsposition at such times as. the B position is come selectable whereby aicall-on a trunk incomvacated, for example,v at night. It is. therefore, ing thereto becomes automatically connected to the object of the invention to increase the efli-. the A operators telephone set. ciency of a dial switching oflice by combining A The B position which is adjacent to an A fifi and call distributing B operators positions upon position may in accordance with a further modi-" a single switchboard and to provide grouping cirfication of the invention be provided with A cord cuitswhereby adjacent A and B operators may circuits in addition to the B position equipment assist each other. hereinbefore described, so that the B operat'ors In accordance with the invention, several arposition serves as a combined A and B position.

35 r n m n f j nt A and B operators posi- In this case theB operators telephone-set is-nortions upon a single switchboard may be made. mally arranged for-answering calls on the A cord Three of such arrangements which are typical, circuits of the combined position and incoming are as follows: a trunk calls are normallybarred from the posi The A operators position which is adjacent tion. If, however, an incoming trunk call is 401 to a call distributing B operators position may awaiting tt ti n th B t may by.de-j 98 be supplied with the usual cord circuits by means pressing a grouping keydisconnect her telephone ofwhich the operator may answer calls for asset from association with herv A. cord circuits sistance-such as intercepted calls and extend such and render her position selectable to the incom-- calls as directed by the calling subscribers. The ing trunk call whereby hertelephone set may be 4.5 -A.operators telephone set of such a position is automatically connected; to the trunk circuit. 100 normally arranged for Connection a y cord Should this .combined Av and. B. positionbe vacircuit of the position by the operation of the cated, the Aroperator whose position is adjacent, listening ke'yof the cord circuit which the opmay by depressing the groupingkeydisconnect erator employs to answer a call. The adjacent hertelephone set from its normal association H 50 call distributing B operators position. may be with cord circuits at her position and render of. the type disclosed in Patent No. 1,753,348, the adjacent combined A and B position selectgranted April 8, 1930 to J. B. Newsom, in which able to incoming trunk calls wherebyan incomcalls from manual oflices of the exchange area ing trunk call may be automaticallyconnected are incoming on trunk circuits terminating in the to such, A operators telephone. set.

' office-in which the A and B operators are located When it isnot desirableto permit, an Al oper ator to assist in answering calls incoming to an adjacent B position, ,the B position may be arranged as a combined A and B position in which the operators telephone set of the combined position is normally associated for answering calls with the A cord circuits of the position, incoming trunk calls being barred. Should a call be incoming on a trunk circuit to this position, the operator may by depressing a position key, disassociate her telephone set from her A cords and render her telephone set automatically selectable to the incoming trunk call.

For the purposes of illustration, the invention has been disclosed as applied to a system in set of the adjacent A position. The invention will be more clearly understood from a consideration of the following description taken in connection with the drawings in which:

Fig. 1 shows a trunk circuit incoming to the A: combined A and B operators position from a distant office and terminating in an incoming selector circuit;

Figs. 2 and 3 show a link circuit, Fig. 2 show- ,ing in the left portion thereof a trunk finder and in the right portion thereof a sender finder,

and Fig. 3 showing an operators position finder; Fig. 4 shows a B operators position circuit; Figs. 5, 6 and TI taken together show a B operators sender;

Fig. 8 shows portions of other link circuits;

Fig. 9 shows the start circuit for initiating the operation of a link circuit;

Fig. 10 shows in the upper portion thereof the B operators telephone and dialing circuits and in the lower portion thereof an adjacent A operators telephone and dialing circuits;

Fig. 11 shows in the upper portion thereof a cord circuit at the B operators position and in the lower portion thereof a cord circuit of anv adiacent A operators position; and

Fig. 12 shows the manner in which Figs. 1 to 11 inclusive should be arranged.

The B operators telephone set shown in the upper portion of Fig. 10 is normally arranged for use with cord circuits suchas the one shown in the upper portion of Fig. 11 which the B operator may use to answer calls incoming from calling subscribers lines requiring intercepted or s'pecial service. To complete such calls the operator plugs into an outgoing trunk jack and dials the required number on her position dial shown in the upper portion of Fig. 10. Should ,there be, however, a call incoming from a distant office over an incoming trunk such as is shown in Fig.1 which would be barred from the position as long as her telephone set is associated with cord circuits, the operator may by the operation of a grouping key, shown in Fig. 10, renoperator uses her keyset shown in the lower portion of Fig. 4 to set theregisters of a sender such as is shown in Figs. 5 to 7 inclusive whereupon the sender proceeds to set the incoming selector in which the incoming trunk circuit terminates and a final selector, not shown, to select the desired line. The final selector may be of the type well-known in the art. The B operator may thus function as a B operator or as an A operator dependent upon whether terminating or originating calls are incoming to her position. Her position thus functions as a combined A and B position.

It is often desirable during periods of light traffic to vacate such combined position and, in accordance with the present invention, this is made possible by providing facilities to enable an operator who normally serves only as an A operator, but whose position may be placed adjacent to the B operators position on the same switchboard, to handle incoming calls requiring the services of the B operator. In the lower portion of Fig. 10 the telephone and dialing circuits of such an adjacent A operators position are disclosed. These circuits are normally associable with cord circuits such as the cord circuit shown in the lower portion of Fig. 11 for handling incoming calls requiring the services of an A operator. position is vacant and incoming trunk calls are barred from such combined position, the adjacent A operator by depressing the grouping key shown in Fig. 10, may when there is an incoming trunk call render the combined position selectable and her telephone set automatically associable for answering such an incoming call.

Trim]: call incoming to combined position from distant oflice In general a subscriber originating a call is answered by an operator known as an A operator who after receiving the called line number, calls upon a B operator for assistance. She does this by inserting the calling plug of her cord circuit in a jack individual to a trunk circuit which terminates in an incoming selector controlled by the B operators equipment. The insertion of the plug in the jack causes the trunk finder of a link circuit to hunt for the incoming selector associated with the jack. As soon as the trunk finder has been started, the B operators position finder is operated to select an idle B operators position. When both have been found two tones called zip tones are transmitted from the B position to the A position and the A operator's headset is connected with the B operators headset so that she may inform the operator of the wanted number. As soon as the idle position is found, the sender finder of the link circuit is actuated to find an idle sender. When this has been found the B operator is signaled and she then operates the keys of her keyset in accordance with the wanted line number. The number is recorded in the sender after which the position is disconnected from the trunk circuit and the sender is connected with the incoming selector to control the setting of that selector and through it the setting of the final selector. When the selectors have been positioned the link circuit is' disconnected and the established circuit is placed under the control of the A operator.

In order to insure quickness and continuity of service, distribution of wear, etc., the trunks terminating in the incoming selectors and the link circuits are arranged in groups. The trunks appear before the trunk finders of the link circuit in the bank of a panel type switch frame.

At such times as an adjacent combined The bank is divided once horizontally into two panels and each panel is divided vertically into two sections so that the terminals in the upper half of one section may be, cross-connected to the terminals of the lower half of the other section. The trunks appearing in the bottom half of one section'are known as the A group of trunks and those appearing in the bottom half of the other section, as the B group of trunks. Each link circuit is represented at the switch frame by a set of brushes, the links terminating in brushes having access to the section of the panel bank in which the A trunks appear at the bottom are called the A group of links and those terminating in brushes having access to the other section are called the B group. Each brush rod carries two sets of brushes, one for each panel. The brush rods are arranged 'on both sides of the panel and the rods on the two sides are driven by different motors. A call on a trunk in the A group will ordinarily initiate the operation of an A link and a call on a trunk in the B group will initiate the operation of a B link. However, the start circuit is so arranged that if all A links become busy and a callis initiated on an A trunk, a B link may be used and vice versa. Likewise, if the trunk finder or the A link fails to find a trunk, a B link will be summoned. If the motor which drives the brush rods of one side of the panel stops, the link circuits on that side are rendered non-usable and the link circuits, on the other side continue operation.

A detailed description of the manner in which calls incoming from a distant oflice are served by the B operator of a combined position will first be given. When the distant A operator plugs into the jack of a trunk extending to the office in which the B operators position is located, a loop circuit is established from the tip of the jack, over the upper left winding of repeating coil 101, the windings of relay 102, the lower left winding of repeating coil 101 to the ring of jack 100 thus causing the operation of relay 102. Relay 102 causes the operation of slow-to-release relay 103 which in turn closes a circuit from battery, winding of slow-to-release relay 104, contact of relay 103, lowercontact of cam 105, (the sequence switch normally standing in position 17 when the trunk is selectable) upper left contact of cam 106 to ground over the lower right and upper left contacts of 'cam 107. Relay 104 uponoperating looks over its right front contact directly under the control of relay 103. Relay 104 indicates .to the start circuit of Fig. 9 that a call has been originated, that is, relay 104.c1oses a start circuit extending from ground at its inner right front contact, right'contacts of cam 108, inher right back contact of relay 109, lower contacts of cam 111, conductor 112 to the contacts of jack 901. Jack 901 is individual to the group of ten trunks to which the trunk of Fig. 1 belongs. From jack 901 the start circuit extends to conductor 911 which is common to the trunks of the subgroup B of the bottom panel of trunk finder 210 111 which the trunk appears and thence by three circuits to battery. One circuit extends through the left winding of relay 921 to battery; a second circuit extends over the inner left back contact of relay 902, right back contact of relay 903;winding of relay 904 and the outer left back contact of relay 905 to battery; while a third circuit extends from the winding of relay 904, outer left back contact of relay 905, winding of relay 903, right back contact of relay 904, right back contact of relay 902 to battery through the right winding of relay 906.

Relay 904 which is individual to the B group of trunks in the bottom panel of finder 210 and relay 921 which is common to the A and B groups of the bottom panel operate in these circuits, but relays 903 and 906 being shunted by battery at the left back contact of relay 905 do not operate. Relay 904 upon operating connects ground over its outer left front contact, the inner left back contact of relay 905 to start conductor 909 for starting a link in search of the calling incoming trunk circuit. It also connects ground over conductor 908 to operate tripping magnets 310 and 311 in preparation for tripping the bottom set of brushes which belong'to the selector finder of the B link allotted to serve the present call. The operation of these magnets, as is well known, operates all of the trip fingers of the group, but only the brushes on the brush rod movedwill be tripped. Relay 904 also opens the circuit of relay 903. Relay 921 in operating starts a timing operation for the purpose of transferring the call to the other subgroup of links if it is not extended within a predetermined length of time and for operating an alarm signal if the call cannot be handled. The operation of the alarm arrangement notbeing pertinent to the present invention, will not be described herein.

The sequence switches of busy links stand in any position from 2 to 8 or 11 to 17 inclusive. If the link circuit is awaiting assignment, the sequence switch stands in position 9 or 18, while the sequence switch of the link assigned for use stands in position 1 or position 10. Assuming that the link shown in Fig. 2 is the next one to be used and therefore has its sequence switch standing in position 1, the circuit traced as above described to conductor 909 may be further tracedv over the inner right back contact of relay 801, upper right and lower left contacts of cam 201, conductor 225 to battery through the winding of relay 202. Relay 202 operates, preparing a locking circuit for itself over its inner left front contact, lower contacts of cam 203, back contact ofrelay 241, conmutator strip 205, brush 206 to ground. Relay 202 also closes a circuit from ground over the upper left and lower right contacts of cam 208, right front contact of relay 202, lower left contact of cam 223, winding of sequence switch magnet 200 to battery. Sequence switch 200 advances to position 2 in this circuit.

When the sequence switch reaches position 1%, ground is connected over the lower right and upper left contacts of cam 222 to the next link. If the next link is in either position 9 or 18 awaiting assignment, this circuit is extended overthe upper right and lower left contacts of earn 203 and the upper left and lower right contacts of cam 201', conductor 225 of such link to battery through the winding of a relay of such link corresponding to relay 202 which upon operating advances the link sequence switch into position 1 or 10 awaiting a call. If the next link is in any position 2 to 8 or 11 to 17, the ground is extended over the upper contacts of earn 222 of such link to assign the next link in the series, .but if it too is busy,'the ground will be further extended over conductor 802, right back contact of-relay 803, left back contact of relay 807, conductor 804 to the next link in the series. If this link and sue; ceeding links are busy, it will be extended over cam 222 of the last link in the series. If this also is busy, the first link to return to the awaiting assignmentnposition will be allotted either from ground applied over the lower contact of cam 222 of that link in position 2, or if no link is in position 2, then from ground over the contacts of cam 224 of the last link, contacts of similar cams of other links, conductor 805, outer left back contact of relay 801, conductor 806, contacts of cam 224', contacts of similar cams of other intervening links, contacts of cam 224 where the circuit is connected to the upper contacts of cam 222 for allotting as previously described. While portions of only four links have been shown, it will, of course, be understood, that as many links will be used as the traflic requires and that the sequential relationship between links extends throughout.

With sequence switch 200 in position 2, the up-drive magnet 230 is operated in a circuit extending over the lower contacts of cam 208, right front contact of relay 202 to ground over the upper contacts of cam 207 for driving the brushes of the trunk finder 210. As the finder 210 is moved upward, magnet 311 trips the brush set. Immediately after starting upward, commutator brush 209 makes contact with segment 211 completing a circuit from ground over brush 209, segment 211, conductor 212, right back contact of relay 301, conductor 302, upper contacts of earn 213, conductor 2l4, winding of relay 905 to battery. Relay 905 operates and looks over its inner 'right front contact, conductor 910, inner right back contact of relay 301, conductor 303 to ground over the upper contacts of cam 218. Relay 905 in operating opens the operating circuit of relay 202, but that relay does not release since its locking circuit is now closed over commutator segment 205. Relay 905 opens the circuit of relay 904 permitting that relay to release in turn releasing tripping magnets 310 and 311.

The incoming selector marks itself as calling by connecting battery through resistance 113, contactsof cam 114, inner left contact of relay 104, outer right back contact of relay 109, conductor 115 to terminal 215. When the selector finder 210 reaches the set of terminals corre sponding to this incoming selector, the circuit is further extended over brush 216, conductor 217, outer left back contact of relay 309, conductor 312, winding of relay 241, upper left contact of cam 219 to ground at the upper right contact of cam 207. Relay 241 operates in this circuit opening the locking circuit of relay 202. Relay 202 does not release until the brushes are properly centered, being held operated. by means of a circuit from battery through the winding and left front contact of relay 202, left contacts of cam 203, commutator segment 220, brush 221 to ground. The release of relay 202 opens the circuit of up-drive magnet 230 bringing the finder to rest on the terminals leading to the calling incoming selector.-

With relay 202 released, it completes a circuit from battery, winding of sequence switch magnet 200, upper left contact of cam 223, right back contact of relay 202, upper contacts of cam 207 to ground. In position 3 the locking circuit of relay 905 extends over the upper right and lower left contacts of cam 218 to ground at the left back contact of relay 202. With the sequence switch in position 3 a circuit is closed from battery, left winding of relay 109, upper contacts of cam 116, outer left contact of relay 104, conductor 117, terminal 226, brush 227, conductor 228, inner left back contact of relay 301, winding of relay 342, outer right back contact of relay 313, conductor 314, upper right contact of cam 219 to ground at the upper right contact of cam 207. Relays 109 and 342 operate, relay '109 opening the previously traced circuit for relay 241 and closing a circuit from battery, winding of sequence switch magnet 110, upper left contact of cam 118, right front contact of relay 109, right contacts of cam 108 to ground at the right front contact of relay 104. Sequence switch 110 advances to position 18. The operation of relay 109 and the advance of sequence switch 110 removes the calling condition from conductor 112, releasing relay 921. Relay 109 remains locked in position 18 over a circuit extending from battery through its left winding, upper left and lower right contacts of cam 119, left front contact of relay 109, lower left and upper right contacts of cam 116, outer left front contact of relay 104, conductor 117 and thence as previously traced to ground. The release of relay 241 permits relay 202 to reoperate in a circuit from battery through the winding of relay 202, conductor 225, left contacts of cam 201, lower contacts of cam 203, back contact of relay 241, commutator segment 205 and brush 206 to ground. Relay 342 upon operating looks over its outer left front contact, conductor 343, the lower right contact of cam 219 to ground at cam 207.

While sequence switch 200 was in position 2, a circuit was completed from battery through the winding of relay 315, right back contact of relay 315, conductor 317, upper left contact of cam 229 to ground at cam 207, which circuit remains closed in position 3. Relay 315 in operating completes one circuit for relay 316 extending from ground at cam 207, upper left contact of cam 229, conductor 317, outer right front contact of relay 315, middle winding of relay 316, conductor 318, upper left and lower right contacts of cam 231, conductor 319, right winding of relay 316 to battery, and prepares a second circuit which extends as previously traced from ground through the middle winding of relay 316, left winding of relay 316, inner left back'contact of relay 320, conductor 321, left contacts of cam 232, conductor 322, right back contact of relay 323 to brush 324 of the position finder 300. Relay 316 is marginally adjusted so that the circuit completed through its right and middle windings does not operate it, but renders it quick to operate when the circuit is completed over brush 324.

It will be assumed that the present system provides one or more B operators positions which are arranged as combined A and B positions and that these positions are all occupied during the busy period of the day. When an operator is present at her position, she inserts her headset plugs 1000 and 1001 into the position jacks 1002 and 1003 completing a circuit from battery through the winding of relay 1004, tips of jack 1003 and plug 1001, through the headset transmitter 1005, tips of plug 1000 and jack 1002,

left winding of repeating coil 1006 to ground. The headset receiver 1007 is also connected over rings of plug 1000 and jack 1002, right back contact of relay 1008, inner left back contact of relay 1009, condenser 1010, right back contacts of relays 1011 and 1012, to the tip talking lead 1013 extending to A cord circuits of the combined position and over rings of plug 1001 and jack 1002, left back contact of relay 1008, upper right winding of repeating coil 1006, outer left back contact of relay 1009 to the ring talking lead 1014 extending to A cord circuits. The B operator with her headset plugged up thus normally functions as an A operator.

Relays 400 to 40 4, inclusive, are relays of a night alarm circuit common to all positions of the Office. With all combined positions thus functioning normally as A positions, there will be no ground connected to conductor 1019 and relay 400 will be unoperated; There will also be' n'o ground on conductor 1020 and relay 4:31 will be unoperated and consequently relay 402 will be operated. 'When therefore, sequence switch 200 of the link circuit reaches position 2, a circuitwill be established from battery -through resistance 346, the winding of relay 320, conductor 329, upper left and lower right contacts of earn 233, conductor 235, front contact of relay 402 to ground through the winding of relay 403. Relays 320 and 403 operate, relay 320 opening the circuit which would otherwise be established upon the operation of relay 315 extending from battery, winding of relay 307,. right back contact of relay 325, outer left back contact of relay 3233, back contact of stepping magnet 308,

, conductor 3 26, upper; right and lower' left cont'actsof cam 2'34, conductor 327, inner right front contact ofrelay 31'5,"le'ft back contact of relay 316 to ground at thefouter left back contacts of relay-3 20, and, therefore relay 307 cannot operate to close the circuit of stepping magnet 308 and the ffinder 300 does not advance to hunt for an -operators position circuit. Relay 403 upon operating cl'oses anob'viou's circuit for relay 404 which inturn closes'a circuit for call awaiting lamp 405 extending from battery through lamp 405,;leftback contact of relay 400 to grwnd at the right front 'COhtaClJ C-f relay 404 and a circuit for night alarm bell 406 extending over the right back contact of relay 400, left front contact of relay 404, through ringing generator at f'Ihe B-operator upon hearing the night alarm bell 406 and seeing the position lamp 405 lighted, depresses her key 1015 thereby closing an obvious circuit for relay-1009 which in turn establishes a circuit extending from battery, winding of relay 1016, inner right contact'of relay 1009 to ground at the front contact of relay 1004 and transfers the operators headset receiver 1007 from the talking leads 1013 and 10 14 extending to her A cord circuits to the talking leads 1017 and 1018 extending to her 13 position circuit. "The operation of relay 1016 also connects ground to conductors 4 1019 and 1020 operating relays 400 and 401'. Relay 400 'upon operating'extinguishes lam 405 and silences the alarm bell 40B and relay4 0'1 upon opcrating releases relay 402which in turn releases relays 4'03, 404 and 320. Assuming that finder 300 is standing with its brushes on the terminals "of vacant position 'circu'it,;relay320 upon re- 'le'as'in'g' closes the previously traced circuit for relay 307 which operates in turn closes a circuit extending from battery, winding of stepping magnet 308, right contact of relay 307 conductor 328, lower contacts of earn 234, conductor'327, thence to'ground-at the-back contacts of relay3 as previously traced. Magnet 308 in operating opens the circuit of relay 307 which releases in turn releasing magnet 308 to step the position finder 300 to the next position.

It will be assumed that the brushes of finder 300 now stand upon the terminals of the position circuit shown and "that the circuit previously traced through the 'windii'i'g of relay 316 to brush 324 now extends throughre'sistance 40s, outer left backcontact of relay 409,-right normal icontacts of key 410, conductor 411 to battery over the inner left front contact of relay 1016. Relay 316 operates and locks in a circuit from battery through its right winding, conductor 319, lower ri ht and upper left contacts of cam 231, 'conduc-- tor 318, left front contact of relay 316 to ground at theleft back contacts of relay 320, in parallel with the circuit previously traced from battery over brush 324, outer right back contact of relay 323, conductor 322, left contacts of cam 2'32, conductor 321, inner left back contact of relay'320, windingand left front contact of relay 316 to grcuncl at the outer left back contacts of relay The connection of ground to brush 324 through the left low'resistance winding of relay marks the position as busy to other links. If

' ch as 316 test a position simultane- -ays may operate, but the attempted closure a locking circuit by one of these relays has a shunting elfect on the other so that both relays release and then the faster relay reoperates and prevents the operation of the other relay and appropriates the position. The operation of relay 316 opens the circuit '0 relay 315 and that relay releases. A circuit is thereupon closed from battery, winding of relay 330; inner left back contact of relay 323, conductor 331, upper left and lower right contacts of cam 236, conductor 332, left back contact of relay 315, right front contact of relay 31'6, conductor 317, upper left contact of cam 229 to ground at cam 207. Relay 330 operates and looks over the inner left back contact of relay 323, outer right front contact of relay 330, conductor 333, right contacts of cam 237, conductor 314, outer front contact ofrelay 342, conductor 343, lower right contact of cam 219 to ground at cam 207 and closes a circuit for operating relay 325 extending from battery, winding of relay 325, inner left front contact of relay 330,'conductor 334, lower left contact of cam 219 to ground at cam 207. Relay 325 operates and closes a circuit extending from battery, winding of sequence switch magnet 200, lower left contact of cam 223, right front contact of relay 202, conductor 204,- middle left front-contact of relay 325, conductor 335, lower left contact of cam 207 to ground for advancing the sequence switch into position 4. j

- -A circuit is now closed from battery, lower right winding of repeating coil 101, winding of supervisory relay 120, conductor 121, left contacts of cam 122, conductor 123, terminal 238 and brush 239 of trunk finder 210, conductor 240, middle left'back contact of relay301, left Winding of relay 336, inner left front contact of relay 325, brush 305 of position finder 300, conductor 33?, winding of relay 412, conductor 413, brush 306,.inner right front contact of relay 325, right Winding of relay 336, outer left contact of relay 325, resistance 338, inner front contact of relay 342, conductor 339, lower contacts of cam 242, conductor S40, outer left back contact of relay 301, conductor 243-, brush 244, terminal 245, conductor 124, left contacts of cam 125, left contacts of earn 126 to ground through the upper right winding of repeating coil 101. Relay 412 operates in this circuit, but the windings of relay 336 are connected at this time differentially and relay 336 does not operate. Relay 412 upon operating closes a circuit from battery on conductor 411, left contact of relay 412, resistance 414, white-capped lamp 415, right back contact of relay 416 to ground at the inner left back contact of relay 417; connects battery over its left front Contact and the right back contacts of relay 417 to the keyset key 450 either directly or through high resistances 418 and 419 and to conductor 421 through low resistance 420 and high resistance 418 and, through the winding of relay Lamp 415 lights and relay 409 operates. Relay 9 upon operating opens the circuit previously traced over brush 324 through the left winding of relay 316 thereby releasing relay 316 since the circuit previously traced through its other winding was opened when sequence switch 200' advanced out of position 3. With relay 316 released, a circuit is established from battery through the winding of sequence switch magnet 200, upper right and lower left contacts of cam 231, conductor 246, left back contact of relay 316, to ground at the outer left back contacts of relay 320 for advancing the sequence switch into position 5. Relay 409 also connects battery through resistances 419 and 434, outer right front contact of relay 409 to conductor 435 and establishes a circuit from battery on conductor 411, over the right normal contacts of key 410, outer left alternate contacts of relay 409, resistance 422, green-capped lamp 423 to ground through interrupter 424 for flashing lamp 423, and establishes a circuit from a source of tone current over its inner right front contact, the back contact of relay 425, back contact of relay 426, right winding of tone coil 427 to ground at the inner right normal contacts of relay 428. This causes a tone current to be induced into the left winding of coil 427 which is connected from conductor 413 over the right front contact of relay 412, outer left back contact of relay 428, left winding of coil 427, outer right back contact of relay 428, condenser 429-to conductor 337. The tone current thus flows over the circuit previously traced through the right windings of repeating coil 101 and is induced through the left windings of this repeating coil over the circuit extending to the A operators position and to her headset. A part of this tone current also flows in a parallel circuit through condenser 430, the intermediate normal contacts of key 410, the outer left back contact of relay 431, conductor 1017, outer left front contact of relay 1009, upper right winding of repeating coil 1006, left back contact of relay 1008, rings of jack 1003 and plug 1001, B operators headset receiver 1007, rings of plug 1000 and jack 1002, right back contact of relay 1008, inner left front contact of relay 1009, conductor 1018, outer right back contact of relay 431, condenser 432. Both the A and B operators hear this tone.

Relay 409 also closes a circuit extending from battery, through the winding of slow-to-operate relay 426, inner left normal contacts of relay 428, inner left front contact of relay 409 to ground on conductor 1020. As soon as relay 426 operates, it opens the circuit through the right winding of tone coil 427 to discontinue the tone and closes a circuit from battery through the winding of slow-to-operate relay 433, left contact of relay 426, inner left front contact of relay 409 to ground on conductor 1020. With relays 426 and 433 both operated, the circuit through the right winding of tone coil 427 is again established and a second tone signal is transmitted to the A and B operators receivers. Relay 433 also closes a circuit from battery, through the winding of slowto-operate relay 425, left contact of relay 433,

inner left front contact of relay 409 to ground on conductor 1020 and after an interval, relay 425 operates, again opening the circuit through the right winding of tone coil 427 to discontinue i the second tone signal. At its left contact, relay 425 establishes a circuit from battery, winding of relay 428, left contact of relay 425, inner left front contact of relay 409 to ground on conductor 1020. Relay 428 operates, looking over its inner left alternate contacts and the inner left frontcontact of relay 409 to ground on conductor 1020, opening the circuit through both windings of tone coil 427 and closing a talking circuit extending from conductor 413, right front contact of relay 412, outer left front contact of relay 428, thence as traced to the B operators headset receiver 1007, returning over the outer right front contact of relay 428, condenser 429 to conductor 337. The A operator may now converse with the B operator to pass the designation of the desired line to the B operator, the A operator having beeninformed by the two tone or zip signals that the B operator is ready to receive such information.

Relay 428 upon operating also connects steady ground to the circuit of lamp 423 over its inner right alternate contacts so that lamp 423 now glows steadily, and opens the circuit of relay 426 which now releases in turn releasing relays 433 and 425. The steady flowing of lamps 415 and 423 is an indication to the B operator that the number is to be passed to her.

It will be recalled that following the selection of the operators position circuit, relay 316 of the link circuit released and advanced'the sequence 105 switch 200 into position 5. Relay 315 now op-- erates in a circuit extending from battery through its winding, the right back contact of relay 316, conductor 317, upper left contact of cam 229 to ground at cam 207 and establishes a circuit from battery through the right winding of relay 316, conductor 319 lower right and upper left contacts of cam 231, conductor 318, middle winding of re lay 316, outer front contact. of relay 315, conductor 317, upper left contact of cam 229 to ground at cam 207 for preparing test relay 316 for operation. A circuit is also prepared from brush 247 of the sender finder 260, right and lower left contacts of cam 232, conductor 321, inner left backcontact of relay 320, left and middle windings of relay 316, outer right front contact of relay 315, thence as traced to ground at cam 207. Relay 315 also closes a circuit from battery through the right winding of relay 344, conductor 341, left contacts of cam 234, conductor 327, inner right front contact of relay 315, left back contact of relay 316 to ground at the outer left back contacts of relay 320. Relay 344 which is slow to operate because of its normally shunted left winding, operates and prepares a holding circuit for itself over its inner right front contact, conductor 345 to centering commutator segment 248. The sender finder to which this commutator belongs normally stands in engagement with some sender which may be busy or idle and therefore brush 249 will be in engagement with an insulating segment of commutator 248. Assuming that the sender is not idle, a circuit will now be closed from battery through the up-drive magnet 252, conductor 253, outer right front contact of relay 344 to ground at the outer left back contacts of relay 320. The sender finger 260 is moved upward under the control of magnet 252 until brush 247 engages the terminal corresponding to an idle sender which is characterized by battery through 1 5 a resistance of 270 ohms.

If the sender finder does not find an idle sender in its upward movement, when it reaches the top of its bank, commutator brush 261 will engage segment 254 closing a circuit from ground over brush 261 and segment 254, upper contacts of cam 233, conductor 329 to battery through relay 320 and resistance 346. Relay 320 operates, opening the circuit of up-drive magnet 252, opening the test circuit through the left and middle windings of relay 316-, opening the circuit of relay 344 and looking over conductor 329, the'left contacts of cam 233, conductor 255 to ground at themiddle right front contact of relay 320. It also closes a circuit from battery, winding of down-drive magnet 256, conductor 257, outer right front contact of relay 320, left back contact of relay 307, conductor 258 to ground over the lower right and upper left contacts of earn 218. The sender finder is therefore restored to normal at which time a circuit is closed from ground over brush 261, normal segment 259, upper right and lower left contacts of cam 262, conductor 263, resistance 346 in shunt of the winding of relay 320, releasing that relay. The release of relay 320 opens the circuit of down-drive magnet 256, restores the circuit of relay 344, the test circuit through relay 316 and the circuit of updrive magnet 252 so that the sender finder may seek further for an idle sender.

'When an idle sender is found, the circuit previously traced through the left and middle windings of test relay 316 to brush 247 is extended over terminal 250, conductor 251, upper back contact of relay-500, inner upper back contact of relay 501, resistance 502 to battery.

Relay 316 operates immediately, opening the operating circuit of relay 344'which releases as soon as its holding circuit is opened at commutator strip 243 to open. the circuit of up-drive magnet 252 to bring the brushes of finder 260 to rest on the terminals of the idle sender. Relay 316 also opens the circuit of relay 315 and that relay releases. When relay 315 closes its back contact, a circuit is closed from ground over the upper left contact of-cam 229, conductor 317, right front contact of relay 316, back contact of relay 315, conductor 332, lower contacts of cam 236, conductor 347, winding of relay 343 to battery. Relay 348 looks over conductor 347, the lower left and upper right contacts of cam 236, conductor 349, right contact of relay 343, conductor 350, brush 264', terminal 265, conductor 266 to ground at the lower back contact of relay 500. Relay 348 also closes a circuit from battery, winding of sequence switch magnet 200, oonductor 351, next to outer left front contact of relay 348, conductor 352 to ground at the right contacts of cam 207, advancing the sequence switch to position 6 in which position relay 343 is held operated in the above traced lockductor 503.

ing circuit. Relay 348 also closes a new holding circuit for relay 330 which extends from battery, winding of relay 330, middle left back contact of relay 323, outer right front contact of relay 33 inner left front contact of relay 348, outer front contact of relay 342, conductor 343, lower right contact of cam 219to ground at earn 207.

When sequence switch 200 reaches position 6 a circuit is closed from ground at cam 207, upper left contact of cam 267, resistance 268, brush 269,

terminal 270, conductor 271 to battery through the winding of relay 501. Relay 501 operates disconnecting battery from terminal 250 for marking the sender as busy and connects ground over its front contact to oil-normal ground 0011- Ground on conductor503 is now extended over the back contact of relay 529, winding of relay 505 to battery. Relay 505 operates closing a circuit from battery through the win'd ing of relay 506, front contact of relay 505, conductor 507; upper back contact of relay 620 to ground on conductor 503. Relay 506 upon operating closesan obvious circuit for relay 508 and a circuit extending from ground on conductor 503, over the inner upper front-contact of relay 506, conductor 509, back contact of relay 624' to battery through the winding of relay 614. Relays 505, 506, 503 and 614 perform no useful function at this'time.

It will be recalled that battery was connected at the position circuit of Fig. 4 to conductors 421 and 435 Conductor 421 is now extended over brush 353, conductor 354, lower contacts of earn 213, conductor 355, outer left front contact of relay 330, inner right back contact of relay 3 13, conductor 356, brush 272, terminal 273, conductor 274, lower back contact of relay 510, winding of relay 511, inner upper normal contacts of relay 512, lower winding of relay 513, conductor 514, lower bacl: contact of relay 704 to ground through the lower windings of relays 701 and 702, and conductor 435 is extended over brush 357, inner right front contact of relay 330, conductor 358, lower left and upper right contacts of cam 275, brush 276, terminal 277, conductor-278, upper back contact-of relay 510, winding of relay 515, thence as traced to ground as previously traced through the windings of relays 513 and 701 and 702. Relays 511, 513 and 515 operate and relays 701 and 702 may also operate, but as soon as relays 511 and 515 operate relay 512 operates in a circuit from battery through its lower winding, front contact of relay 515, front contact of relay 511 to ground on conductor 503 and looks from ground on conductor 503 through its upper winding and inner upper alternate contacts in series with the circuits traced through the windings of relays 511 and 513 to battery at the position circuit, opening the previously traced circuit extending through the lower windingof relay 513 and the lower windings of relays'701 and 702 and these relays will release. Relay 512 also closes a circuit from battery through the windings of relays 724 and 725 in series, conductor 706, lower front contact of relay 512 to ground on conductor 503. Relay 725 looks itself and relay 724 over its upper contact to ground on conductor 503 and in turn extends ground from conductor 503 over its lower contact in series through the windings of relays 715 and 714 operating of relay 516, resistance 517, conductor 518, lower winding of relay 600, conductor 606, upper alternate contacts of relays 724, 714, and704, conductor 607, upper winding of relay 513, inner upper. back contact of relay500, conductor 282,

terminal 279, brush 230, conductor 281, outer left front contact of relay 348, outer right front contact of relay 325, brush 359, conductor 436, winding of relay 437, left back contact of relay 438, right back contact of relay 416 to ground at re-' lease key 439. Relay 437 operates, looks over its outer left front contact, inner left front contactof relay 409 toground on conductor 1020 and is closed from battery, inner upper back contact closes a circuit for relay 438 extending from battery onconductor 411, left contact of relay 412, winding of relay 438, left front contact of relay 437, thence to ground as traced on conductor 1020. Relay 438 upon operating looks over its left front contact and the left back contact of relay 416 to ground at key 439, extends ground on conductor 1020 over its inner right front contact to battery through the winding of relay 417 and opens the initial operating circuit of relay 437. Relay 417 upon operating opens its right contacts thereby disconnecting battery from conductors 421 and 435 releasing relays 511, 515 and 512 in the sender. Relay 512 upon releasing closes a circuit extending from battery, lower back contact of relay 519, winding of relay 516, conductor 520, lower front contact of relay 625, conductor 521, lower back contact of relay 512 to ground on conductor 503. Relay 516 upon operating looks over its next to inner lower front contact, conductor 521, lower back contact of relay 512 to ground on conductor 503 and at its inner upper back contact removes battery from the circuit previously traced through the winding of relay 437 at the position circuit.

Relay 437 upon releasing connects conductor 606 as previously traced to conductor 436, thence through the left winding of relay 440, inner right back contact of relay 437, outer right front contact of relay 438, resistance 441 to the keyset 450 and extinguishes the white-capped lamp 415, which was maintained lighted over the outer right front contact of relay 437 after the operation of relay 417, as a signal that the sender is attached and ready to record digits of a desired line designation. For the purpose of more readily identifying the registration control circuits extending from the operator's keyset 450 to the sender, the first of these circuits which will be hereinafter referred to as the No. 1 circuit extends from resistances 419 and 434 at the position circuit, over the outer right front contact of relay 409, conductor 435, thence as traced to conductor 278 in the sender. The second circuit which will be hereinafter referred to as the No. 2 circuit extends from resistances 418 and 420, over conductor 421, thence as previously traced to conductor 274 in the sender, and the third circuit which will be hereinafter referred to as the No. 3 circuit is established from resistance 441, outer right front contact of relay 438, right back contact of relay 437, left winding of relay 440, conductor 436 and thence as previously traced to conductor 282 in the sender.

At the position circuit the No. 1 circuit may be extended through low resistance 434 and the right contacts of key No. 1 or No. 6 to conductor 442 which is connected to battery on conductor 411 over the left contact of relay 412 or through low resistance 434 and high resistance 419 and the right contacts of key No. 2 or No. 7 to conductor 442. Circuit No. 2 may be extended through low resistance 420 and the right contacts of key No. 3 or No. 8 to conductor 442 or through low resistance 420 and high resistance 418 and through low resistance 441 and high resistance ,that either circuit No. 1 or No. 2, or neither,

will be completed by the operation of any keys, but not both.

-At the sender circuit No. 1 extends at this time from conductor 278, over the upper back contact of relay 510, winding of relay 515, inner upper normal contacts of relay 512, lower winding of relay 513, conductor 514, lower alternate contacts of relays 704, 714 and 724, conductor 707, lower windings of thousands register relays 601 and 602 to ground. Circuit No. 2 extends from conductor 274, over the lower back contact of relay 510, winding of relay 511, inner upper normal contacts of relay 512, lower winding of relay 513, thence as traced through the lower windings of relays 601 and 602 to ground. Circuit No. 3 extends from conductor 282, inner upper back contact of relay 500, upper winding of relay 513, conductor 607, upper alternate contacts of relays 704, 714 and 724, conductor 606, lower winding of thousands register relay 600, conductor 518, upper alternate contacts of relay 516, lower back contact of relay 512 to ground on conductor 503.

Should the operator depress a key before the sender has been connected to the position and the registration circuits above traced are ready, a circuit is closed from ground through the right winding of relay 416, outer right back contact of relay 438, outer left back contact of relay 417, through either low resistance 441, or both resistances 441 and 443, through the left contacts of the depressed key to battery over conductor 442. Relay 416 operates and transfers the circuit of lamp 415 from direct ground at the inner left back contact of relay 417 to ground through interrupter 444 thus warning the operator that she has started to set up the number prematurely.

By operating key 439 she may release any falsely operated relays of the sender and also restore the circuit of lamp 415. When the sender is ready, lamp 415 will be extinguished as previously described and she may proceed to set up the number.

Assuming for the purposes of illustration that the called line number is 3456, the operator will successively operate keys Nos. 3, 4, 5 and 6. From the circuits above traced for the completion of the three registration circuits, it will be seen that the operation of key No. 3 extends circuits No. 2 and No. 3 to battery through low resistance. The completion of circuit No. 3 operates relay 440 which looks over its right winding and front contact to ground on conductor 1020. Relay 440 in operating extends the circuit of meter 445 to the locking ground of relay 440. Since circuit No. 3 is completed no matter which key is operated and relay 440 looks as soon as operated, it will be apparent that the depression of a key by an operator in the completion of a call will register once on the peg count meter 445.

At the sender since circuit No. 2 was completed, relays 511, 513 and 602 will be operated and since it was completed through low resistance 420 only, marginal relay 601 will be operated. The operation of relay 602 closes an obvious circuit for relay 604. The operation of relay 511 closes a circuit from ground on conductor 503, front contact of relay 511, upper back contact of relay 512, conductor 608, inner lower front contacts of relays 704, 714 and 724, conductor 708 to battery through the winding of relay 603. Relay 603 operates, locks through resistance 609, upper front contact of relay 603 to ground on conductor 521 and closes an obvious circuit for relay 605. Relays 601 and 602 look through their upper wind-- ings and inner upper front contacts to ground on conductor 521. The completion of circuit No. 3 through low resistance 441 alone causes the operation of marginal relay 600 which looks over its upper winding and inner upper front contact to ground on conductor 521. Relay 513 also operates and closes a circuit from ground on conductor 521 over conductor 522, inner upper front contacts of relays 704, 714 and 724 to battery through the winding of relay 724. Relay 724 is thus held operated, but relay 725 is shunted by ground connected to both terminals of its winding and releases. When key No. 3 is released, relay 513 releases in turn releasing relay 724. The release of relay 724 transfers the registration circuits Nos. 1, 2 and 3 to the hundreds register relays 720 to 723 inclusive.

The depression of the key No. 4 extends circuit No. 2 from battery on conductor 442, through high resistance 418, in addition to resistance 420, and extends circuit No. 3 from battery on conductor 442, through low resistance 441. Therefore, relays 511, 513 and 722 are operated in circuit No. 2 and relays 513 and 720 in circuit No. 3, while the operation of relay 511 closes circuit for relay 723. Relays 720 and 722 1 ck over their upperwindings and inner upper front contacts to ground on conductor 521 and relay 723 locks through resistance 716 and its upper front contact to ground on conductor The operation of relay 513 extends a circuit from grounded conductor 522, over the inner upper front contacts of relays 704 and 714, inner upper back contact of relay 704 to battery through the winding of relay 714 for holding relay 714 operated and shunting relay 715 which When key No. 4 is released, relay 714 also releases extending circuits Nos. 1, 2 and 3 to s register relays 710 to 713 inclusive.

The peration of key No. 5 completes circuit No. 3 through both high resistance 443 and low resistance 441 to battery on conductor 442. Therefore, relay 513 alone is operated, none of the register relays 710 to 713 being operated. The operation of relay 513 connects ground over conductor 522, the inner upper front contact of relay the inner upper back contact of relay 714 to battery through the winding of relay 704 shunting and releasing relay 705. When the No. 5 key is-released, relay 704 also releases extending the Nos. 1, 2 and 3 registration circuits to units register relays 700 to 703 inclusive.

The depression of key No. 6 completes circuit No. 3 through both high resistance 443 and low resistance 441 to battery on conductor 442 and circuit No. 1 through low resistance 434 only to battery on conductor 442. Relays 515, 513, 701 and 702 operate over the No. 1 circuit, but due to the high resistance in the No. 3 circuit relay 700 does not operate, but relay 513 operates. The operation of relay 513 connects ground over conductor 522, inner upper back contact of relay 704, conductor 717, resistance 626 to battery, shunting relay 625 and releasing that relay.

If the B operator depresses a wrong key and realizes it before she has depressed the last key corresponding to a particular number, she may release the sender by operating key 439. By doing so she releases relay 433 which in turn releases relay 417. Relay 417 upon releasing relights lamp 415 and connects battery to the No. l and No. 2 registration circuits thereby causing the -ecus operation of relays 511 and 515 in which does not occur when she operates any of the numerical keys. 7 With relays 511 and 515 both operated, a circuit is closed from ground on conductor 503, front contacts of both of these relays to battery through the lower winding of relay 512. Relay 512 in operating extends the circuits of these relays through its upper alternate contacts and upper winding to ground on conductor 503 and disconnects ground from conductor 521 with the result that all operated register relays release. Relay 501, however, does not release since it is held to ground at the link circuit and the senderis held busy and cannot be selected by another link. When key 439 is released, the position and sender circuits function to prepare themselves for the registration of the correct number as previously described.

. When the last key of the keyset 450 is released and relay 513 releases a circuit is closed from ground on conductor 521, back contact of relay 513, lower front contact of relay 516, conductor 523, back contact of relay 625, conductor 524, winding of relay 510.to battery. Relay 510 operates and locks to ground on conductor 521 and closes an obvious circuit for relay 500.

The operation of relay 500 removes ground from conductor 26 6 thereby releasing relay 348 in the link circuitwhich in turn releases relay 330. Relay 330 in turn releases relay 325. A circuit is now established from battery, inner upper front contact of relay 516, winding of relay 519, lower front contact of relay 510, conductor 274, terminal 273, brush 272, conductor 356, inner back contact of relay 313, left back contact of relay 330, conductor 361, upper left and lower right contacts of cam 242, conductor 340, outer left back contact of relay 301, conductor 243, brush 244, terminal 245, conductor 124, left contacts of cam 125, left contacts of cam 126, upper right Winding of repeating coil 101 to ground. Relay 519 operates looking directly from battery at its lower alternate contacts and releasing relay 516. Relay 516 upon releasing establishes a circuit extending from ground over conductor 521, upper back contact of relay 516, outer right normal contacts of relay 525, inner upper front contact of relay 500, conductor 282, terminal 279, brush'280, conductor 281, outer left back contact of relay 348, conductor 360, lower contacts of cam 201, conductor 225 to battery through the winding of relay 202. Relay 202 operates and closes a circuit for advancing sequence switch 200 into position 7 which may be traced from battery, winding of magnet 200,

lower left contact of cam 223, right front contact of relay 202, lower right and upper left contacts of cam 208 to ground; When the sequence switch leaves position 6 the holding circuits of relays 109 and 342 are opened and these relays release, relay 109 closing a circuit for advancing sequence switch 110 into position 1 which extends from battery through the winding of magnet 110, lower left contact of cam 118, inner right back contact of relay 109 to ground over the lower left and right contacts of cam 128. As sequence switch 110 advances out of position 18 the circuit of relay 519 is opened and relay 519 releases. The circuits of incoming selector 150, link circuit and sender are now ready for fundamental selections.

When relay 325 released it in turn released relay 412 in the position circuit which in turn released relays 409, 417, 428, 438 and 440 and extinguished lamps 415 and, 423 freeing the operators position circuit to receive another call.

With sequence switch 110 in position 1 and 

